challis



P. CHALLIS.

TRUNK PISTDN.

APPLICATION FILED MAR. 16. 1920.

1,396,504; gamma Nov. 8, 1921.

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APPLICATION FILED MAR. 16, 1920- 1,396,504.. 7 Patented Nov. 8 21.

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Q o s Q P. CHALLIS.

TRUNK PISTON.

APPLICATION FILED nun. 16, 1920.

1,396,504. Patented Nov. 8, 1921.

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/UNITED STATES PATE T. OFFICE.

PHILIP oHALLIsoF LONDON, ENGLAND.

TRUNK-PISTON.

To all whom it may concern;

Be it known that I, PHILIP CrrALLrs, a subject of the King of England, residing at London, England, have invented certain new and useful Improvements in Trunk- Pistons, of which thefollowin'g is a specification. A

This invention has reference to trunkpistons, more particulary intended for internal combustion engines but the invention is applicable to pistons for steam and other engines. form the skirt with slots extending upward from the bottom with a view to obtaining a resilient lower portion to the piston.

It is the principal object of the present invention to provide a piston the whole of the contact area of which is resilient, flexible or yielding, the contact area being of such dimensions, and so positioned intermediately of the length of the piston as to prevent penetration of the oil-film by the piston under the cross-head resultant thrust. This is attained by providing the contact area either as a single intermediate contact zone extendingaxially along the greater part of the piston trunk above and below the gudgeon pin, or as two or more such zones positioned above and below the said point. At these zones clearance is suppressed by resilient, flexible or yielding surfaces, which in the free state are preferably of larger diameter than the bore of the cylinder. These intermediate zones are located Substantially midway between the'upper and.

. A piston having these features. i 'here-. inafter referred to as having a skirt of' barrel-shape, by which. I mean a skirt which is of greater. diameter at its central zone than at either extremity, the variation in diameter taking place by bulging lines which give theshape of anordinary barrel, resembling the geometrical body known as a central frustum of a sphere, spheroid, ellip- Spe'cification of Letters Patent.

In these pistons, it is known to.

' piston from any tilting Patented Nov. 8, 1921.

Application filed'March 16, 1920. Serial No. 366,368.

soid or. the like solid or surface; the curved generating lines of such solid or surface may be replaced by connected straight lines approximating thereto in which case the bulging portion or barrel will have the form of two frusto-conical zones on opposite sides of a central. cylindrical zone. The barrel portion of the skirt is so positioned that its greatest diameter comes approximately at the level of the piston pin bosses and the contacting or guidin area provided by the inward closure of the resilient barrel-pop tion extends therefore above and below the level of the said bosses, thus restraining the movement in relation to thecylinder an thereby preventing piston slap as well as knocking due to the reversal of stress. Instead ofproviding a single over-size barrel-form area level with the piston pin bosses, I may provide two or moresuch zones or areas, for example, one above and one below said bosses, whereby the same restraining action is produced. The over-size contact surfaces extend circumferentially around the piston skirt through the entire circle of 360 degrees, so thatthe. piston is held accurately central with the cylinder walls. Morever, by the present arrangement having the contact areas substantially midway of the length of the piston, the latter is maintained at all times co-axial with the cylinder, without looseness of either the head or the lower end, and consequently no tilting of the piston, beyond that due to the yield of the resilient zones as the lateral thrust pressure varies, can take place to cause the piston to pivot and bring its head-end violently across from one side to the other by reason of the transfer of the cross-head thrust.

The invention is hereinafter described with reference to the accompanying drawings in which Figure 1 is a transverse section of an interna-l combustion engine trunk piston.

Fig. 2 is an elevation at right angles to Fig. 1, one half in section.

Figs. 3 and 4 are sections similar to Fig. 1; of alternative constructions.

Figs. 5and 6 are details showing the section of the sleeve providing the contact zone, according to two modifications of the inven tion.

Fig. 7-is an elevation of a piston having the contact zone afforded by a surface integral with the piston.

Fig. 8 is a sectional elevation of Fig. 7.

The piston a is provided at b with one or more barrel-shaped portions, either integral with the body as in Figs. 7 and 8, or consisting of sleeves or bands 0 attached in any suitable manner, and slotted at (Z to afford resilience in a radial direction to facilitate circumferential expansion and contraction.

In Figs. 1 and 2, the piston a is fitted with two barrelshaped portions, an upper and a lower one, such barrel-shaped ortions 6 being-slitted or slotted at (Z to a 0rd the resilient-zones and such slits or slots in all cases stopping short of the head a and the lower edge a of the piston. The dotted lines 6 in Fig. 1, represent in an exaggen ated degree the curvature of these barrelshaped portions before introduction of the piston into the cylinder. The sleeve is pret erably attached by screw threads 0 as in Figs. 1 and 2, or a flange c and ring-nut 0 as in Fig. 4, at one portion or extremity, while its free. extremity 0 is a sliding fit upon the supporting surface a of the pis ton body. In Fig. 3, the sleeve 0 is connected tov an upper shouldered portion 0 providing the piston-ring lands and is secured by a. ring-nut 0 upon the aluminium Jody a.

The slots cl do not extend to the lower edge a of the skirt of the piston; such edge remains continuous and is of narrower dimeter than the largest diameter of the barrel-shaped portion Z).

The slots (Z may be arranged parallel to the axis of the piston, like the joints between staves of a barrel, as shown in Figs. 7 and 8, or alternatively they may be oblique, as shown in Figs. 1 and 2; the slots may intersect or meet at their extremities. so as to afford flexible tongues and may be of the same width throughout or-wider at the middle or some other portion of their length, as desired. The slots may be ended by transverse perforations or holesd (Fig.8) through the trunk of the piston, and theseholes may be used for connecting together two or more slots. Flexibility may also; be obtained by providing one or more rows. of holes (Z as shown. in Fig. 6,01 by milling out or otherwise forming grooves (Z or thin places partly through the wall of the piston or sleeve, as shown in Fig. 5.

It will. be noted that the barrel-shaped portion may be integral with or rigidly secured to the piston body or one of its ends may be. secured to the piston body so as not to move either axially or radially relatively to the piston body although it may sometimes not be rigidly held from r0 tary movement.

In the constructions illustrated in Figs. 1 to i, the piston 1s. of the built-up type, for

example with an ordinary head a and parttrunk a of the usual metal for pistons, and an attached skirt containing the barrelshaped portion I) of some more spring-y metal, as pressed steel.

The barrel-shaped portion is of slightly larger diameter than the bore of the cylinder so that when in place it is pressed in radially by the containing walls; by its outwardly expanding action it therefore floats, the areas containing the oil-film being large enough to prevent the oil from being crushed out, and by the. outwardly expanding action aforesaid, it prevents. tilting of the piston at the ends of its stroke or chattering during the stroke. One or more grooves (Z may be. cut in the spring barrel to retain lubricant and allow a suiiicient degree of flexibility even when a thick gage of metal has been employed, and a scraper-ring preferably non-floating can be mounted in such an annular groove. l have indicated at e annular grooves around the head end of the piston. to receive packing rings of the usual construction, the rings themselves beingomitted as being well known in the art. Any suitable form of packing means may however be employed to make the piston gas-tight.

The external diameter of the barrel-shaped portions in the case for example of a piston for internal combustion engines, in which the cylinder is of four-inch diameter, may be live one-.thousandths over the cylinder size, while the body of the piston may vary from eleven and a half one-thousandths under cylinder size at the head end to four and a half one-thousandths under cylinder size at the upper extremity of the barrel shaped portion.

In the case of a three-inch piston, the actual diameters-at the points 1 to 9 in Fig. 7 may be as follows I..'

1 four one-thousandths under cylinder size.

2 and 3 three onesthousandths under cylinder size.

l thirty oneethousandthsunder cylinder size. r

5 and 9 two onesthousandths under. cylinder size. 7

6 and 8 exact cylinder size inch What I claim is 1. A piston, comprising a head, and a V skirt, said skirt having an annular proing rod, an intermediate portion of said skirt being convexed to form an annular protuberance extending axially above and below the level of said attachment means.

3. A piston, comprising a head, and a skirt, said skirt being convexed to form an annular protuberant portion intermediate of its length and said protuberant portion being slotted to afford resilience.

4. A piston, comprising a head, and a skirt, the intermediate portion of said skirt being convexed to form an annular protuberant portion and being resilient to allow yield in a radial direction.

5. A piston, comprising a head, a skirt, and means for the attachment of a connecting rod, said skirt being of larger diameter at intermediate points above and below the level of said attachment means than at its ends. I

6. A piston, comprising a body portion, a head, and a sleeve having a circumferential protuberance, said sleeve rigidly connected at one extremity to said body and yieldably supported therefrom at the other extremity and constituting a skirt to said piston.

7. A piston, comprising a head, and a skirt, said skirt being slotted to afford a plurality of contact strips bearing upon the cylinder wall intermediately of the length of the piston, and said skirt being of larger 7 diameter over the central portions of said strips than at its ends.

8. A piston, comprising a head, and a skirt, said skirt being slotted intermediately of its length, and contact strips formed by the slotted portions of said skirt, said contact strips extending radially outward at their central portions to a larger diameter than at their ends.

9. A piston, comprising a head, a body portion, means for attaching a connecting rod to said body portion, and a sleeve secured to said body portion, said sleeve having a circumferential protuberance and slotted longitudinally to afford resilient contact strips bearing upon the cylinder Wall in proximity to the level of said attaching means.

10. A trunk-piston, comprising a head portion, a skirt portion having a continuous lower edge, and an intermediate trunk-portion, said intermediate trunk-portion being resilient both above and below the gudgeon pin bearing, and being also of larger diameter than either said head portion or the continuous edge of said skirt portion.

11. A trunk-piston, comprising a head portion, a skirt portion having a continuous edge, a gudgeon pin bearing arranged intermediately of the length of said skirt portion, said skirt portion both above and below the gudgeon pin bearing being resilient and also of larger diameter than either the head portion or the continuous edge of said skirt portion.

12. A piston comprising a head, a body portion, means for attaching a connecting rod, guide surfaces for said piston adapted to slide on the walls of a cylinder, said guide surfaces extending around the circumference of said piston above and below said attaching means and bein of diameter not less than that of said cylinder.

In testimony whereof I have aflixed my signature in presence of two witnesses.

PHILIP OHALLIS.

Witnesses:

Vro'ron F. FEENY CYRIL J. FEENY. 

